In present day, tools, for example, wear resistant tools such as cold forging and warm forging tools, e.g., punches and headers, and cutting tools require wear resistance and sliding properties, as well as fracture resistance. These tools employ techniques that improve wear resistance, sliding properties and fracture resistance by forming various coating layers on the surface of a substrate of a hard material such as a WC-based hard metal, TiCN-based cermet, ceramics, diamond or cBN.
As the coating layer, a TiCN layer and a TiAlN layer have been generally widely employed. Various measures have been taken to bring about higher wear resistance and improve fracture resistance.
For example, Japanese Unexamined Patent Publication No. 2001-293601 describes a cutting tool having on the substrate surface thereof a wear-resistant coating that contains at least one type of ultrafine particle compound having an extremely high hardness selected from the group consisting of B4C, BN, TiB2, TiB, TiC, WC, SiC, SiNx (x=0.5 to 1.33) and Al2O3. This publication discloses that the hardness of the coating is improved by containing the ultrafine particle compound.
Japanese Unexamined Patent Publication No. 10-251831 discloses a hard coating layer having the structure that a Ti oxide, an Al oxide and an M oxide are dispersion distributed in a TiAlMN-based substrate by forming a TiAlMN-based hard coating layer, followed by heat oxidation treatment.
Japanese Unexamined Patent Publication No. 2002-129306 discloses a composite hard coating in which the coating is enhanced by dispersing TiAlN composite nitride dispersed particles having a different composition ratio from the coating matrix, and dispersed particles such as TiAlVN, TiAlZrN, TiAlCrN or the like, each containing a different element from the coating matrix, into a TiAlN-based hard coating.